With the development of electronic industry, many circuits demand control stability in addition to the original function. Refer to FIG. 1 for an example. In order to verify the current of an inductor 301 in a buck-boost power conversion circuit 300, the current industry uses a Hall element 302 to undertake measurement, wherein the Hall element 302 is cascaded to the inductor 301 to acquire the inductor current. However, the Hall element 302 is usually bulky, occupying more layout space and unfavorable to miniaturization of the electronic devices. Besides, the Hall element 302 is more expensive and will raise the overall cost of the circuit.
A US patent No. 2016/0036326 disclosed a power supply control circuit, which comprises an emulator circuit. The emulator circuit includes a first input terminal and a second input terminal. The first input terminal receives a first input value. The first input value indicates the magnitude of an input voltage used by a power supply circuit, whereby to generate an output voltage for loads. The second input terminal receives a second input value. The second input value indicates the magnitude of an output voltage generated by the power supply circuit. In the prior art, the emulator circuit uses the input voltage and the output voltage to simulate an inductor current flowing through the power supply circuit. Although the prior art can acquire the value of the inductor current, the circuit thereof is very complicated and unfavorable for application.